1. Field of the Invention
The present disclosure relates generally to increasing the functionality of a computer USB port and, more specifically, to extending a USB port in conjunction with KVM extension products.
2. Description of the Related Art
Typically, a standard computer interface, or a keyboard, video display and a mouse (KVM), must be located close to the computer to which it is attached. A keyboard/video/mouse (KVM) extender enables a computer interface to be located at a greater distance from the computer than is typically possible with a standard interface. For example, a company can place all its employees' computers in a rack-mounted system in a locked room and yet still provide a standard KVM interface at each employee's desk. To the employee, it appears as though the computer is still located at the employee's desk. This centralization of computers enables companies to maintain tighter security over their computers and also simplifies the computers' maintenance by locating them in a single place.
In addition, a KVM switch can enable multiple computers to be accessed by means of a single set of keyboard, video display and mouse. This is convenient in the situation in which a user accesses multiple computers such as an application server, a web or email server and a game box. With a KVM switch, the user can access multiple computers with a single interface, thus reducing the cost of both components and maintenance.
Although, the KVM extension mode of operation typically supports some standard user I/O protocols, or “legacy” protocols, such as PS/2, analog video, and serial communications, a universal serial bus (USB) connection presents several problems. Most interface extensions such as KVM use simple, low frequency data rates and protocols, whether using either analog or digital signal types. However, USB has a very complex signaling protocol, data packet structure and electrical specification, as well as short latency requirements. The USB standard requires strict adherence to these transaction latency and electrical requirements, which limits the USB extension distance, rather than allow the several hundred meters of a typical KVM mode. In addition, the USB requirements prevent the use of a KVM switch because a switch may degrade the USB signaling and further reduce the overall extension distance. One method of providing USB connectivity over a KVM connection is to switch the native USB signals into KVM extension media and then simply “tune” the transmission to try and achieve 100–200 meters of extension distance. However, there is no guarantee that this type of tuning will achieve the desired result. Another method of extending USB connectivity over a KVM connections is to extend an entire peripheral component interconnect (PCI) bus with a PCI-PCI bridge.
KVM interfaces also enable multiple users to simultaneously access a single computer system. Old methods of accomplishing this include switching PS/2 keyboard and mouse interfaces or physically passing a keyboard and mouse from user to user. One obvious disadvantage of the these old methods is that all but one user is blocked while another user controls the computer.
Many other problems and disadvantages of the prior art will become apparent to one skilled in the art after comparing such prior art with the present invention as described herein.
The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the figures, like reference numerals designate corresponding parts throughout the different views.